Graves' disease is a common human autoimmune disorder caused by autoantibodies that stimulate the TSH receptor (TSHR). There are no spontaneous animal models of the disease. We will use two induced mouse models; "naked" TSHR-DNA vaccination, and the "Shimojo" approach (injecting TSHR-expressing fibroblasts). With these models, we will analyze the following issues in the immune response to the TSHR:- 1. Influence of micro-organisms or lack of self tolerance: We will study the titers and functional activity of TSHR antibodies induced by TSHR-DNA vaccination in combination with microbial products, as well as in TSHR-knockout mice that cannot acquire self tolerance to the TSHR. 2. Cytokine and cellular interactions: Wild type mice and B-cell knockout mice will be used to determine (a) which cytokines are produced by splenocytes challenged with TSHR-protein; (b) whether CD4+ or CD8+ T cells are involved in the response; (c) if B cells are required to induce memory T cells specific for the TSHR, 3. Epitopes recognized by TSHR-specific T cells: Synthetic TSHR peptides will be used to determine the epitopes recognized by T cells (a) cloned from TSHR-DNA vaccinated BALB/c mice; (b) TSHR knockout mice that lack tolerance to the TSHR; (c) mice transgenic for HLA that predispose (DR3) or protect against (DQ6) Graves' disease. Naturally processed TSHR peptides will also be studied, 4. Co-stimulatory signals: The role of co-stimulatory molecules will be explored (a) in vitro by using antibodies to block CD40/CD40-1igand and CD28/B7-1/2 interactions; (b) in vivo using mice with disrupted genes ("knockouts") for CD28, CD40, B7-1 or B7-2; (c) in vivo by injecting mice with anti-B7-1 (or control) together with TSHR -fibroblasts (that express B7-1). 5. Role of TSHR cleavage and shedding: We will test the hypothesis that TSHR cleavage followed by shedding of the heavily glycosylated A subunit plays a role in the immune response to the TSHR:- (a) using DNA encoding a non-cleaving or shedding TSHR; (b) examining binding of the heavily glycosylated TSHR A-subunit vs less glycosylated antigens (such as TPO) to the mannose receptor that captures glycosylated organisms for presentation to T cells.